Enzymes are widely used in industry to convert one chemical substance into another, e.g. degrading proteins into amino acids (proteases) or producing sugar from plant cell walls (hydrolytic enzymes). While a constitutively active enzyme is generally useful in industrial settings, in specific applications it can be beneficial to tightly control enzyme activity. For example, if a protease can be inactivated while in storage, it will not autodegrade (Stauffer and Treptow 1973, Russell and Britton 2002). For hydrolytic enzymes expressed in plants, enzyme activity during growth can harm the plant (Gray et al. 2011, Shen et al. 2012). If the enzyme is inactivated until the plant is harvested, then the plant can grow normally. Upon activation the enzyme can degrade the plant cell wall. In many cases, temperature can act as a convenient exogenously controllable parameter of a system.
Controlled dimerization has previously been used to bring together two different proteins, change the fluorescence character of a protein, or block the accessibility of a substrate binding pocket (Spencer et al. 1993; Nagai et al. 2001; Zhou et al. 2012). Chemical inducers of dimerization have been used effectively to control transcription of target genes, triggering specific signal transduction, and recruit proteins (Spencer et al. 1993; Spencer 1996; Amara et al., 1997).